Method of separating particles contained in a laden fluid, and a dynamic separator for performing this method

ABSTRACT

A method and apparatus for separating particles from a fluid, wherein the particle-laden fluid is subjected to centrifugal force to cause a radial movement of the particles and fluid adjacent a radial surface of a rotating filtering partition disposed at right angles to its axis of rotation. A suction is applied through the partition to cause an axial movement of the fluid through the partition for separating the fluid from the particles.

United States Patent 1191 Bourdlal at. 19, 1974 [5 METHOD OF SEPARATINGPARTICLES 3,679,035 7/1972 Schmitt 210/404 X CONT IN A LADEN FLUID, ANDA 3,606,735 9/1971 Baigas, Jr 210/404 X DYNAMIC SEPARATOR FOR PERFORMING3,491,886 1/1970 Glos et al 210/331 THIS METHOD FOREIGN PATENTS ORAPPLICATIONS [76] Inventor: Lucien R. Bourdal, 30, Arehue 1,216,08812/1970 Great Britain 210/78 Aristide Briand, Arpajon. France 22 Filed:No 22 1971 Primary Examiner-Samih N. Zaharna Assistant Examiner-F. F.Calvetti 1 1 p N05 200,846 Attorney, Agent, or Firm-Woodhams Blanchardand Flynn [30] Foreign Application Priority Data Nov. 23, 1970 France70.41908 [57] ABSTRACT 52 us. 01 210/78 210/330 210/345 A methOd andaIP11aratus Separating Particles fmm 210/398 210/402 a fluid, whereinthe particle-laden fluid is subjected to 51 Int. Cl ..B01d 21/26centrifugal cause a radial movement 5 Field of Search 210/7 4 39 402 404particles and fluid adjacent a radial surface Of a rotat- 21O/407 330,331, 360 A, 345 346 347 ing filtering partition disposed at right anglesto its axis of rotation. A suction is applied through the partition [56]References Cited to cause an axial movement of the fluid through theUNITED STATES PATENTS partition for separating the fluid from theparticles.

3,625,366 12/1971 Gan-one 210/330 4 Claims, 4 Drawing Figures 1 1. 5 2 1l l 5 El 14 l0 n? f 1a 6 1 11 25 PATENTEU MAR l 9 I974 SHEEI 1 OF 2PATENTEDHA'R 19 IBM 3 797' 663 SHEET 2 BF 2 METHOD OF SEPARATINGPARTICLES CONTAINED IN A LADEN FLUID, AND A DYNAMIC SEPAMATOR FORPERFORG THIS METHOD The present invention concerns a method ofseparating particles contained in a laden fluid, in which method theladen fluid is subjected to the action of a centrifugal field. Theinvention also relates to a dynamic separator for performing this methodand of the type comprising a rotor located in a fluid-tight enclosureembodying an inlet for the particle-laden fluid, an outlet for thepurified fluid and, in its lower part, an outlet for the particles, thisrotor carrying a filtering cartridge of generally cylindrical formmounted coaxially with the axis of rotation of the rotor.

, Known separation methods which merely employ the action of acentrifugal field are generally not completely efficient. This is thecase, for example, with separators of the cyclone type. If it isrequired to obtain complete efficiency it is necessary also to employ afiltering partition. Then however, there arises the problem of caking,and loss of pressure varies with the thickness of the caked material.However, known arrangements employing a centrifugal field and afiltering partition do not enable suspended particles to be separatedfrom a fluid containing them on a continuous basis and with apractically constant loss of pressure, in the most economicalconditions. In fact, in all these systems, the fluid and the particlesmove in opposite directions at a given moment and thus cause a furtherloss in pressure. In certain conditions, sometimes even resulting inresonance phenomena, the loss in pressure, instead of remainingconstant, increases at a very rapid rate, so that it is necessary tointerrupt the circulation of the fluid from time to time in order toremove from the rotating assembly a considerable portion of theincreasing mass of particles which participate in the rotary movement,and in order thus to recreate conditions in which normal resistance isoffered to the fluid along its centripetal path; alternatively it mayeven be necessary to clean or replace the filtering cartridge. This isthe case, for example, with assemblies known under the name of rotaryfilters. Finally, it is often necessary to resort to supplementarycleaning operations such as clearing by vibration, counter-currentairblowing, flushing of the cartridge, etc.

The aim of the present invention is to overcome these drawbacks and toachieve this the object of the invention is to provide a filteringmethod which is mainly characterized in that it consists in setting up asuction action which is applied through a filtering partition caused torotate with the fluid and which occurs in a direction different fromthat imposed upon the particles by the centrifugal field.

A dynamic separator of the above-mentioned type for performing thismethod is characterized in that the filtering cartridge has at itscenter an upstream space, connected in a fluid-tight manner to the inletfor the laden fluid, and is constituted by a succession of filteringpartitions arranged in such manner as to form, alternately, on one handradial passages directly connecting the upstream space to the spaceoutside the rotor and, on the other hand, transverse passages which areseparated from the radial passages by filtering partitions, throughwhich transverse passages the purified fluid is extracted as a result ofa vacuum on suction created between the inlet and the outlet for thefluid, these transverse passages extending into a downstream space inthe rotor connected in a fluid-tight manner to the outlet for thepurified fluid incorporated in the enclosure.

Because of this arrangement, the particles suspended in the laden fluidare subjected not only to drag by the fluid, but particularly to theaction of the inertia resulting from the centrifugal field of the rotor.They are thus carried directly through the radial passages from the axisof the rotor to its periphery and then accumulate by gravity in thelower portion of the enclosure at the same level as that of the outletfor the particles.

As regards the purified fluid, this first follows a centrifugal pathsubstantially parallel with the filtering surfaces which then curvesapproximately through an angle of at the moment when the fluid passesthrough these filtering surfaces into the downstream space.

Consequently, the fluid and the particles never travel in oppositedirections as they do in the known arrangements, and this facilitatescontinuous cleaning of the filtering surfaces. The separator of theinvention is thus enabled to operate on a continuous basis with avirtually constant loss of pressure.

In one embodiment of the invention, the filtering partitions aredisposed in planes perpendicular to the axis of rotation of the rotor.

Furthermore, the filtering cartridge is constituted by a certain numberof filtering blocks of parallelepiped form uniformly spaced along theperiphery of the rotor and separated from each other by spaces in theform of triangular prisms into which the transverse passages extend,said spaces communicating with an annular chamber in the rotor, whichchamber is connected in a fluid-tight manner to the outlet for thepurified fluid.

An embodiment of the invention will now be described by way of exampleand by reference to the attached drawings, in which:

F IG. 1 is a vertical axial section through a dynamic filtering systemin accordance with the invention;

FIG. 2 is a section on the line lI-II of FIG. 1;

FIG. 3 is a section through part of the system and on the line Ill--lllof FIG. ll; and

FIG. 4 is a partial perspective view on a greater scale of one of thefiltering blocks with which the system is equipped.

The filter illustrated in FIGS. 1 to 3 is mainly constituted by a rotorl fitted inside a fluid-tight enclosure 2 of generally cylindrical form,its axis extending horizontally. The rotor l, which is likewise ofcylindrical form, is solidly connected to a horizontal shaft 3 ofcruciform cross-section and mounted at its ends to rotate in bearings 4each of which is provided in the lateral checks of the enclosure 2. Oneof the ends of this cruciform shaft 3 also projects outwardly of theenclosure and carries a grooved pulley 5 which enables the rotor 1 to beturned at the required speed by means of a motor, not illustrated.

The fluid-tight enclosure 2 contains three separate openings, namely aninlet 6 for a particle-laden fluid that is to be purified, an outlet 7for the pruified fluid, and an outlet 8 for the particles. The inlet 6for the laden fluid extends into a first annular chamber 9, hereinaftercalled the upstream chamber," formed on one of the lateral checks of theenclosure and disposed around the cruciform shaft 3, whereas the outlet7 for the purified fluid extends into another annular chamber 10,hereinafter called the downstream chamber, formed in an identical manneron the other cheek of the enclosure. The outlet 8 for the particles islocated at the bottom of the enclosure 2 and at the end of a kind ofhopper 11.

The rotor 1 is fitted with a filtering cartridge which is hereconstituted by six filtering blocks 12 of parallelepiped form fittedbetween two circular plates 13 and 14. These six filtering blocks areevenly spaced in a hexagonal arrangement over the periphery of the rotorand thus form at the center of the rotor an upstream space 15surrounding the cruciform shaft 3. The plate 13, that is to say theplate which is situated at the side where the inlet 6 for the fluid islocated, is mounted on the cruciform shaft 3 by way of a circularopening 16 formed at its center, this opening thus enabling the upstreamchamber 9 of the enclosure to communicate directly with the upstreamspace 15 in the rotor. The second plate 14 also has at its center acircular opening through which the shaft 3 passes, but this opening issealed in a fluid-tight manner by a disc 17 rigidly secured to the plateand at the same time solidly connecting the rotor to its driving shaftso that the two rotate together.

Between the plate 14 and the corresponding cheek of the enclosure 2there is located a third circular plate 18 connected to the first twoplates by the cylindrical wall 19 of the rotor. This third plate 18,together with the plate 14, defines an annular downstream chamber 20,the function of which will be explained in more detail hereinafter. Thedownstream chamber 20, formed in this manner in the rotor, communicatesdirectly with the downstream chamber in the enclosure 2 by means of thecruciform shaft 3 which extends through the plate 18 by way of acircular opening 21 as in the case of the plate 13.

Furthermore, sealing elements 22 are provided in line with the bearings4 between the plates 13 and 18 respectively and the corresponding cheeksof enclosure 2, so as to provide perfectly sealed communication, on theone hand, between the inlet 6 for the laden fluid and the upstream spacein the rotor through the upstream chamber 9 in the enclosure, and on theother hand, between the downstream chamber in the rotor and the outlet 7for the purified fluid through the downstream chamber 10 in theenclosure. It will also be seen that the plate 13 is detachably securedto the cylindrical wall 19 of the rotor by means of a flange 23 so thatfiltering blocks 12 may be introduced into the interior of the rotor andreplaced when necessary.

As can be clearly seen from FIG. 2, the two filtering blocks 12 areseparated from each other by spaced 24 in the form of triangular prisms.These prismatic spaces 24 communicate directly with the downstreamchamber 20 in the rotor by way of triangular openings 25 cut in theplate 14, which plate thus has an apertured form as illustrated in FIG.3. It will also be seen that the cylindrical wall 19 of the rotor alsocontains apertures in line with the filtering blocks 12 as shown at 26in FIG. 2, for a reason which will be explained later. Thus, between thetwo plates 13 and 14 material of the wall 19 is present only in linewith the prismatic spaces 24 which are thus open only at those of theirsides presented to the plate 14 and facing the chamber 20.

A description will now be given of the method of forming the filteringblocks 12 with which the system of the invention is equipped, byparticular reference to FIG. 4 which illustrates in perspective and on alarger scale a portion of one of these blocks.

It might first be mentioned that the filtering blocks 12 are mainlyconstituted by a stack of rectangular filtering partitions 27 arrangedperpendicularly to the axis of rotation of the rotor l, the material andtexture of these partitions being selected according to the fluid andparticles to be treated. These filtering partitions 27 are separatedfrom each other by ribs so positioned as to form, on the one hand,radial passages 28 directly connecting the upstream space 15 in therotor to the space outside the rotor through openings 26 provided forthis purpose and, on the other hand, transverse passages 29 leadingdirectly into the prismatic spaces 24. Furthermore, these passages 28and 29 alternate with each other in a regular manner and communicatewith each other only through the filtering partitions 27. It will infact be seen from FIG. 4 that each radial passage 28 is blocked at thesides presented to adjacent prismatic spaces 24 by two lateral ribs 30,whereas each transverse passage 29 is blocked at the side presented tothe upstream space 15 in the rotor and at the side presented to theopenings 26, by two lateral ribs 31.

The filtering system according to the invention and described aboveoperates in the following manner:

As in all filtering systems, the downstream cycling of the upstreamfluid, that is to say, movement of the fluid from the inlet 6 toward theoutlet 7 is caused by a difference in pressure as these two openingsobtained by any suitable known means. Also the rotor is caused to rotatecontinuously at a predetermined speed by means of the grooved pulley 5mounted on the shaft 3 and it thus creates a centrifugal field.

The particle-laden fluid admitted through the inlet port 6 first entersthe upstream annular chamber 9 in the enclosure 2 and thence passes tothe upstream space 15 in the rotor l by way of the circular opening 16surrounding the cruciform shaft 3.

The fluid then enters the filtering blocks 12 through the radialpassages 28 and then first follows a centrifugal path substantiallyparallel with the filtering partitions 27. This path then curvesapproximately through an angle of at the moment when the fluid passesthrough the filtering partitions into the downstream chamber 20 in therotor 1, by passing successively through the transverse passages 29, theprismatic space 24 and the triangular openings 25 in the plate 14. Fromhere, the fluid purified in this manner moves into the downstreamchamber 10 of the enclosure by passing through the circular opening 21surrounding the cruciform shaft 3, and is discharged through the outletport 7.

The particles that are suspended in the fluid and are unable to passthrough the filtering partitions 27 are subjected not only to the dragof the fluid but in particular to the inertia resulting from thecentrifugal field of the rotor. Furthermore, this inertia increases asthe particles move away from the axis of the rotor whereas dragdiminishes.

Under the action of these two forces, the particles are carried directlythrough the radial passages 28 and the openings 26 from the axis of therotor to the space outside the rotor and they then accumulate by gravityin the hopper 11 where they are discharged periodically or continuouslyby means of a known device, not illustrated, located at the outlet 8.

It will be seen from the foregoing that the fluid and the particlesnever travel in opposite directions as they do in known apparatus. Thisresults in continuous and efficient cleaning of the filtering partitions27, which enables a filtering system in accordance with the invention tooperate on a continuous basis and with a practically constant loss ofpressure.

It might also be pointed out that the drag exerted by the fluidcomprises, on the one hand, a component which is parallel with thefiltering partition and is thus a useful component, and, on the otherhand, a component which is perpendicular to this wall and which isharmful since it tends to bring particles into contact with thepartition or at least with the cake which, as is well known, forms onthe partition when the pores in the partition are of smaller size thanthose of the largest particles entrained in the fluid. Steps shouldtherefore be taken to reduce as much as possible the value of theharmful component in the drag, which value will mainly depend upon thearea of the filtering partitions in relation to the required throughputof fluid.

As regards the useful component of the drag exerted by the fluid, it isknown that it diminishes progressively with increasing distance from theaxis. Normally, it fades out completely or almost completely near theperiphery of the rotor since the fluid has then passed downstreamthrough the filtering partitions. It would however be possible to bringabout intentionally a certain leakage upstream in the case where inertiaalone is insufficient for causing all the particles to be carried along.This leakage may then be recycled through the filter after total orpartial separation of the particles carried therein, or it may simply bedischarged into the atmosphere, depending upon the requirements of theparticular case.

Preliminary separation may be necessary before the fluid enters thefiltering zone, so as to remove excessively large particles which mightblock the open spaces 28 between the filtering partitions 27.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A method of separating particles from a fluid laden therewith,comprising the steps of providing a rotatable filter unit having asubstantially planar filtering partition, rotating said unit about anaxis which is substantially perpendicular to the plane of said filteringpartition, supplying a particle-laden fluid to said filter unit adjacentthe radially inner end of said filtering partition, subjecting theparticle-laden fluid to centrifugal force as caused by rotation of saidunit to cause an outward radial movement of the particles and fluidadjacent one radial surface of the rotating filtering partition,applying a suction adjacent the other radial surface of the partition tocause movement of the fluid through the partition in a directionsubstantially parallel to said axis for separating the fluid from theparticles, and moving the remaining particles radially outwardly pastthe radially outer end of said partition.

2. A dynamic separator for separating particles from a particle-ladenfluid, said separator having a rotor located in a fluid-tight enclosureembodying an inlet for the particle-laden fluid, an outlet for thepurified fluid and, in its lower portion, an outlet for the particles,the rotor carrying a filtering cartridge of generally cylindrical formand coaxial with the axis of rotation of the rotor, comprising theimprovement wherein the filtering cartridge has at its center anupstream space connected in a fluid-tight manner to the inlet for theladen fluid, the cartridge being constituted by a succession offiltering partitions arranged to form, alternately, on one hand, radialpassages directly connecting the upstream space to a space outside therotor and, on the other hand, transverse passages which are separatedfrom the radial passages by filtering partitions, through whichtransverse passages purified fluid is extracted as a result of a suctioncreated between the inlet and the outlet for the fluid, the transversepassages extending into a downstream space in the rotor connected in afluidtight manner to the outlet for the purified fluid.

3. A dynamic separator according to claim 2, wherein the filteringpartitions are disposed in planes perpendicular to the axis of rotationof the rotor.

4. A dynamic separator according to claim 3, wherein the filteringcartridge is constituted by a selected number of filtering blocks ofparallelepiped form uniformly spaced around the periphery of the rotorand separated from each other by spaces in the form of triangular prismsinto which the transverse passages extend, said spaces communicatingwith an annular chamber in the rotor connected in a fluid-tight mannerto the outlet for the purified fluid.

2. A dynamic separator for separating particles from a particle-ladenfluid, said separator having a rotor located in a fluid-tight enclosureembodying an inlet for the particle-laden fluid, an outlet for thepurified fluid and, in its lower portion, an outlet for the particles,the rotor carrying a filtering cartridge of generally cylindrical formand coaxial with the axis of rotation of the rotor, comprising theimprovement wherein the filtering cartridge has at its center anupstream space connected in a fluid-tight manner to the inlet for theladen fluid, the cartridge being constituted by a succession offiltering partitions arranged to form, alternately, on one hand, radialpassages directly connecting the upstream space to a space outside therotor and, on the other hand, transverse passages which are separatedfrom the radial passages by filtering partitions, through whichtransverse passages purified fluid is extracted as a result of a suctioncreated between the inlet and the outlet for the fluid, the transversepassages extending into a downstream space in the rotor connected in afluid-tight manner to the outlet for the purified fluid.
 3. A dynamicseparator according to claim 2, wherein the filtering partitions aredisposed in planes perpendicular to the axis of rotation of the rotor.4. A dynamic separator according to claim 3, wherein the filteringcartridge is constituted by a selected number of filtering blocks ofparallelepiped form uniformly spaced around the periphery of the rotorand separated from each other by spaces in the form of triangular prismsinto which the transverse passages extend, said spaces communicatingwith an annular chamber in the rotor connected in a fluid-tight mannerto the outlet for the purified fluid.